The Royal Navy is the naval branch of the military forces of the United Kingdom. With 91 commissioned vessels, it is considered the world's second most powerful navy in terms of global force projection, after the United States Navy.[1][2] As of November 2006, the Naval Service (including the Royal Marines) had 38,710 regular personnel.

During the Napoleonic Wars the Royal Navy played a major role, reaching the height of its achievements at the Battle of Trafalgar in 1805, where a British fleet commanded by Lord Nelson decisively defeated a combined French and Spanish fleet. During the remainder of the 19th century the Royal Navy became the world's dominant naval force and played a major part in building and defending the British Empire. In 1906 HMS Dreadnought became the Royal Navy's first "all-big-gun" battleship, a key turning point in British naval history; subsequently, large battleships became the dominant form of sea-power.

In both the First World War and Second World War, the Royal Navy played a key role in keeping the United Kingdom supplied with food, despite German attempts at a naval blockade using submarine warfare. After the Second World War, during the Cold War years, the disintegration of the British Empire forced Britain to downsize its navy, while the United States Navy took on the major role as the world's dominant sea power. The Royal Navy was re-organised with a strong emphasis on anti-submarine capabilities in the North Atlantic Ocean, to counter the potential threat of the Soviet Union.

In 1982, the Royal Navy was the principal British force in the Falklands War. The British submarine HMS Conqueror, a nuclear-powered submarine, sank the Argentine cruiser ARA General Belgrano during this conflict, the first time in naval history that a nuclear-powered submarine had engaged an enemy ship with torpedoes.